Many apparently healthy people may have insufficient levels of vitamin K2, says a new study, potentially increasing the risk of bone loss and also for hardening of the arteries.
Analysis of 896 blood samples collected from 110 healthy participants revealed that both children and adults had high levels of under-carboxylated species of osteocalcin (ucOC) and matrix Gla protein (dp-ucMGP), proteins specific to bone and heart health, respectively, and said to be biomarkers of vitamin K insufficiency and deficiency.
Additionally, vitamin K2 (menaquinone-7, MK-7) supplementation at different states of vitamin K deficiency showed that children and adults with the highest vitamin K deficiency responded most to K2 supplementation.
“Children and adults above the age of 40 years showed the largest vitamin K2 deficiency, and accordingly may benefit from MK-7 supplementation to improve their vitamin K2 status,” said lead investigator Elke Theuwissen of VitaK.
Hogne Vik, CEO of NattoPharma, which provided the K2 supplements for the researchers, said the study demonstrates a general vitamin K2 deficiency in the whole population.
“Supplementation with vitamin K2 (MenaQ7) improves the status of the biomarkers correlating with a normal vitamin K2 level in the body that is especially important for bone development in children and for delaying development of osteoporosis and vascular calcification in adults from the age of 40 years onward,” he said.
The study supports previous findings from researchers at the University of Maastricht's VitaK & Cardiovascular Research Institute CARIM that raised an “intriguing question” as to whether, “all (or: most) apparently healthy adults are sub-clinically vitamin K deficient”.
There are two main forms of vitamin K: phylloquinone, also known as phytonadione, (vitamin K1) which is found in green leafy vegetables such as lettuce, broccoli and spinach, and makes up about 90% of the vitamin K in a typical Western diet; and menaquinones (vitamins K2), which make up about 10% of Western vitamin K consumption and can be synthesized in the gut by microflora.
Menaquinones (MK-n: with the n determined by the number of prenyl side chains) can also be found in the diet; MK-4 can be found in animal meat, MK-7, MK-8, and MK-9 are found in fermented food products like cheese, and natto is a rich source of MK-7.
Implications for RDAs
The new study’s authors note that the recommended dietary allowance (RDA) for vitamin K is based on clotting factor synthesis needed by the liver, but significant levels of undercarboxylated Gla-proteins are found in the circulation (ie. beyond the liver) of people not taking supplements. “This suggests that vitamin K intake above the RDA is required for an optimal extra-hepatic vitamin K status,” they added.
Source: Food & Function
Published online ahead of print, doi: 10.1039/C3FO60464K
“Vitamin K status in healthy volunteers”
Authors: E. Theuwissen, E.J. Magdeleyns, L.A.J.L. M. Braam, K.J. Teunissen, M.H. Knapen, I.A.G. Binnekamp, M.J.H. van Summeren, C. Vermeer